Protein synthesis, degradation, and retention: mechanisms of indeterminate growth in cephalopods.

This study is the first to examine the underlying process of growth in a cephalopod, the southern dumpling squid (Euprymna tasmanica), to ascertain the mechanism by which indeterminate growth is achieved in this live-fast, die-young group of animals. This is the first study to estimate rates of protein synthesis and growth of squid from 7 to 140 d of age, providing an understanding of both the pattern and the process of growth throughout the lifetime of a squid species. Younger and smaller individuals had greater rates of protein synthesis and protein synthesis retention efficiency, as well as more RNA, than did older and larger individuals. Variation in growth rates among older, larger individuals was a function of individuals with faster growth rates having greater protein synthesis retention efficiency and also greater concentrations of protein. Critically, growth did not cease in the adults and, with an average of 10% of protein synthesized being retained, the mechanism to support the nonasymptotic growth model of cephalopods is provided.